An array is an object with components arranged according
to a rectilinear coordinate system.
In principle, an
array in Common Lisp may have any number of dimensions, including zero.
(A zero-dimensional array has exactly one element.)
In practice, an implementation may limit the number of dimensions
supported, but
every Common Lisp implementation must support arrays of up to
seven dimensions.
Each dimension is a non-negative integer; if any dimension of an array is zero,
the array has no elements.

An array may be a general array, meaning each element may be any Lisp
object, or it may be a specialized array, meaning that each element
must be of a given restricted type.

One-dimensional arrays are called vectors. General vectors may contain
any Lisp object. Vectors whose elements are restricted to type
string-char are called strings. Vectors whose elements are
restricted to type bit are called bit-vectors.

X3J13 voted in March 1989 (CHARACTER-PROPOSAL)
to eliminate the type string-char and to redefine the type
string to be the union of one or more specialized vector
types, the types of whose elements are subtypes of the type character.